The present invention relates generally to the transmission of electromagnetic waves and, more specifically, to a new class of light processors and guiding structures having enhanced light transmission, modulation, and processing capabilities.
The development and utilization of optics for focusing radiation in imaging and communications systems is essential. Numerous imaging and communications systems include means for generating and utilizing highly directive and intense beams of substantially coherent, high frequency, electromagnetic wave energy in the visible light and adjacent energy bands. In view of the high frequencies of such waves and the broad frequency range over which they are operative, a need exists for means for limiting the spreading of the beam between source and receiver, and thereby minimizing attenuation in energy received at the receiving station.
Solid lens designs are utilized in conventional imaging and communications systems to focus light between a transmitting radiation source and a detector whereby input having relatively wide line spread function is focused by the lens into an output beam of light having a relatively narrower line spread function. The output light may then be directed to a recording device and thereafter processed by suitable electronics into an image or display. Lenses in conventional solid state imaging systems are formed of material demonstrating desired optical properties. Such solid-state lenses can either comprise a discrete lens element or a bundle of optical fibers arranged to collect input light and focus the light into a focused beam to be processed as described above.
The use of solid lenses or bundles or optical fibers for the purpose of focusing abeam of electromagnetic radiation has not proven entirely satisfactory because of the substantial attenuation that results from even the highest optical quality lenses or fibers; attenuation that results from even the highest optical quality lenses or fibers; attenuation resulting from impurities or defects in the lens or fibers or from unavoidable losses at the surface interface due to reflection. The bending o light rays essentially requires establishing a refractive-index gradient transverse to the path of radiation. Due to surface scattering at the lens surface, or fiber bundle, interface and at any refractive-index variant boundaries within the lens, conventional solid lenses or fiber bundles result in an unacceptably high attenuation level and a relatively low signal to noise ratio.
In order to obviate the performance limitation so solid lens or fiber optic bundle configurations, gas lens designs have been proposed and utilized in systems for focusing radiation. Gas lenses may use a thermal gradient to create a suitable index of refraction and thereby narrowly focus the input beam. An alternative approach in known lens devices is to achieve a lensing effect by the creation of density gradients in a gas or gases, whereby creating layers of gas having different indices of refraction. U.S. Pat. No. 4,582,398 discloses one such gas lens configuration. The gas lens disclosed in the ""398 patent provides a gradually changing index of refraction rather than the stepped gradient index of refraction when solid optics are employed. U.S. Pat. No. 4,740,062 shows yet another alternative known gas lens utilizing multiple jets of gas, each gas having a different index of refraction. The enclosure containing the gas jets is positioned to intercept a light beam that passes through the enclosure and directs the input beam through the gas jet interfaces to achieve the intended convergence of the beam
While the gas lens designs discussed above work will and represent a viable alternative to solid optics, certain shortcomings attend their use. First, deployment of such a system requires relatively large volumes of gas in order to achieve the dynamic jet streams required to lens input radiation. Secondly, the containment system of the lens is relatively complex, bulky, expensive to manufacture, and difficult to maintain in proper adjustment in order to function as intended. In addition, while capable of transmitting large amounts of radiation, such gas lenses are relatively weak and prove inadequate for many applications.
U.S. Pat. No. 5,682,268 discloses yet another variation in a gas lens comprising apparatus for focusing a beam of electromagnetic radiation. The device creates spark gaps disposed within a space through which radiation passes. Shock waves produced by the electric discharges in a gaseous medium at the spark gaps interact to form a localized region of high pressure in the gaseous medium centered on the optical axis of the beam of electromagnetic radiation. The gaseous medium thus is caused to have a density profile capable of bringing the beam of electromagnetic radiation to a focus. A cylindrical chamber conlines the shock waves and includes co-axial apertures that allow the passage of the electromagnetic radiation through the chamber.
The above device alters the density of the gaseous medium to alter the optical properties thereof. While, in theory, the shock waves caused by electrical discharges can achieve a desired density variation, controlling the precise density of the gaseous medium can prove problematic in achieving a practical light processing system.
It has further been proposed to vary the pressure of a gas within a lens assembly in order to adjust the focal length of the lens to the value required. U.S. Pat. Nos. 4,732,485; 4,758,072; and 4,331,388 disclose such lens configurations. While working well, the lens assemblies are relatively complex and remain dependent on the performance and quality of the solid state lens elements of the assembly to achieve acceptable performance.
It is, therefore, an object of the invention to provide a new class of light processors and optical guiding structures for lightwave applications.
It is another object to provide a new class of light processors and optical guiding structures having enhanced focusing properties.
It is a further object of the invention to provide a class of lenses for electromagnetic radiation having a novel lens media.
Yet a further object of the invention is to provide a class of light processors and optical guiding structures that provide a low level of blurring and a higher signal to noise ratio for enhanced performance in imaging applications.
Another object of the invention is to provide a class of light processors and optical guiding structures capable of providing a relatively high signal to noise ratio for increased bandwidth for communications applications, at variable wavelength response.
Still a further object of the invention is to provide a class of light processors and optical guiding structures capable to modulate, amplify, process, shape, focus, direct, route, polarization-control, or switch an incident light beam.
Still a further object of the invention is to provide a class of lenses for electromagnetic radiation having a novel lens media that may be readily varied to achieve an optimal focal length.
These and other objects of the present invention, as well as the advantages thereof over existing prior art electromagnetic radiation lenses, which will become apparent from the description to follow, are accomplished by the improvements hereinafter described.
In general, the present invention provides light processors and optical guiding structures that can be operated at low or high pressures with and without an applied electric field, dopants, or gas mixtures. If no applied field is utilized, the gas cell operates in the passive mode. Increasing or decreasing the concentration of dopants and the gas pressure within the cell changes the index of refraction and the transmission/frequency response properties of the structure. In order to optimize the performance of the cell, the gas cell may be embedded with polar molecules or other impurities. The use of different dopants, gas mixtures, or impurities as a transmission media, all with different indexes of refraction, will allow transmission of light through reflections, blocking also certain wavelengths. In the active mode of operation, an electric field may be applied across the gas cell. Upon application of the electric field, the dipole moment of the polar molecules will align to the direction of the electric field and will increase the local electric field. Light incident on the lens system will couple to the local electric field created by the polar molecules and enhanced focusing will result. Consequently, when utilized in imaging applications, less blurring and a high signal to noise ratio results. In communications applications, the higher signal to noise ratio translates into increased bandwidth. The dipole constituent of the gas cell may be achieved by polar gas molecular dopants, impurities, gas mixture, or a polar primary gas within the cell may be utilized. The composition and physical parameters of the gas may be changed so as to optimize the focal length of the lens and its frequency response.
According to a further aspect of the invention, a method of processing light for lightwave applications is disclosed comprising the steps of interposing a gas cell in a path followed by the light, the cell having an enclosure composed of substantially transparent material, a gas medium contained within the enclosure, and polar molecules/impurities/gas mixtures dispersed within the gas medium; applying an electric field across the gas cell; and aligning the polar molecules to the direction of the applied electric field to contribute to an effective dielectric constant. In order to further optimize the system, the pressure of the gas medium may be varied to change its effective index of refraction.
A preferred exemplary embodiment and method incorporating the concepts of the present invention is shown by way of example in the accompanying drawings without attempting to show all the various forms and modifications in which the invention might be embodied, the invention being measured by the appended claims and not by the details of the specification.